Centrifugal pump



Jan. 4, 1966 G. J. HAARHUIS 3,227,039

CENTRIFUGAL PUMP Filed April 21, 1964 2 Sheets-Sheet 1 INVENTOR.

GERARDUS J. HAARHUIS G. J. HAARHUIS GENTRIFUGAL PUMP Jan. 4, 1966 2Sheets-Sheet 2 INVENTOR.

GERARDUS J. HAARHUIS Filed April 21, 1964 United States PatentCENTREFUGAL PUMP Gerardus Johannes Haarhuis, Emmasingel, Eindhoven,

Netherlands, assignor to North American Philips Company, Inc., New York,N.Y., a corporation of Delaware Filed Apr. 21, .1964, Ser. No. 361,351Claims priority, application Netherlands, Apr. 23, 1963, 291,870; Aug.29 1963, 297,303 1 Claim. (0]. 103--103) The invention relates to acentrifugal pump adapted to pump boiling liquids, such as liquefiedgases, which comprises .a casing containing one or more rotatableimpellers each accommodated in a separate space. The said spaces areeach provided with an inlet aperture communicating with the centralportion of the relevant impeller containring one or more ducts for theliquid which extend from the centre to the periphery of the impeller.Each impeller is surrounded "by a guide duct for the liquid and to thisduct a discharge spout is connected, at least in a pump containing asingle impeller.

As is known, in pumping boiling liquids by means of pumps of the kindunder consideration vapour bubbles are formed at the suctionend. Toprevent an excessive amount of this vapour from entering the pump, suchpumps are usually provided with means through which the excess vapourmay escape before being entrained into the pump by the liquid. 'If thevapour enters the pump, the volume delivered and the raising height ofthe pump are adversely affected.

It has now been found that not all the vapour produced during suction isdischarged, but that part thereof is entrained into the pump by theliquid and interferes with satisfactory operation of the pump.

'In a known pump provided with an impeller, endeavours have been made toovercome the above-mention-ed disadvantage by providing the part of thecasing opposite the vanes with a row of apertures.

A -furtherdisadvantage of known pumps of the kind .under considerationconsists in that such pumps operate only if the liquid at the suctionend is under a given ninimum pressure (minimum suction height). If thelevel of the liquid in the container from which the liquid is pumpedfalls to .a value such that the pressure of the liquid at the suctionend falls below the said minimum pressure, excessive vapour lbubbleformation occurs and prevents satisfactory operation of the pump. Thisimplies that with the known pumps a considerable amount of liquid isalways left in .theicontainer.

Surprisingly, it has now been found that the abovementioneddisadvantagesare overcome if according to the invention at least the liquid guideduct surrounding the first impeller through which the liquid passesand/or the liquid discharge spout connected to this guide duct isprovided with one or more apertures in its outer wall.

Through these apertures a small stream of the liquid and vapourcontained in the liquid guide duct is continuously discharged. If anexcessive amount of vapour collects in the liquid, the delivery pressureof the pump falls off. This is prevented by the apertures according tothe invention in that the pump is continuously flushed.

When the vapour has disappeared from this flushing liquid, the lattermay be returned to the suction end of the pump. This flushing actionprovides quiet operation of the pump which continues to deliver untilthe level of the liquid has fallen to the inlet aperture of the pump.Consequently the pump according to the invention has a minimum suctionheight equal to zero.

A further advantageous embodiment of a centrifugal pump according to theinvention, which is provided with a shaft on one end of which at leastone impeller is mounted while the other end may be coupled to a drivingdevice, is characterized in that when the shaft is arranged in avertical position, the apertures open into the upper portion of theliquid guide duct and/or the liquid discharge spout.

A favourable embodiment of the centrifugal pump according to theinvention which includes a single impeller, is characterized in that the'wallof the liquid guide duct is provided with at least one aperture .atan .area immediately preceding the area where the liquid guide ductmerges into the liquid discharge spout.

:In a further advantageous .embodimentof the centrifugal pump inaccordance with the invention the wall of the liquid guide ductsurrounding the first impeller through which the liquid passes isprovided with an annular recess into which the aperture or aperturesopens oropen and into which at one side a slit between a wall of theimpeller and the upper wall of the chamber containing the impeller opensand which at the other side merges in the liquid guide duct.

The annular recess ensures a ready flow of vapour to the aperture orapertures for exhausting this vapour. The annular recess acts as .aperipheral channel for collecting vapour which from this channel can how.to theexhaust aperture or apertures. It has been found that theoperation of the pump is much less satisfactory if the annular recess inaccordance with the invention is omitted.

:In order that the invention may readily be carried into effect,embodiments thereof will now be described, by way of example, withreference to the accompanying diagrammatic drawings, in which:

FIGURES 1 and 2 are an axial sectional view and a plan view respectivelyof a single-stage centrifugal pump and FIGURES 3 and 4 are :twosectional views, taken at right angles .to one another, :of .amulti-stage centrifugal pump.

In FIGURES 1 and 2 a pump casing is designated by the-referencenumeral 1. This pump casing .comprises a lower cover 2 and an uppercover 3. The .upper cover 3 bears guiding means .4 fora pump shaft 5.The guiding means 4 is provided with inlet apertures .6 for the liquidto be pumped. The pump shaft 5 carries an impeller 7. This impeller '7is :provided with four liquid ducts 8 which extend from the innercircumference of the impeller .to its periphery. It will be appreciatedthat :the :number of liquid ducts may be different in different pumps.The

impeller is provided with sealing means 9 in :the upper .cover 30f thepump casing.

The periphery of the impeller 7 is surrounded by .a liquid guide duct:16 which terminates in a liquid discharge spout 11. A liquid dischargepipe may be connected to this spout.

At an area immediately preceding the area where the liquid guide duct 10merges into the liquid discharge spout 11, an aperture 12 is provided.This aperture 12 is disposed so as to open into the upper portion of theliquid guide duct 10 in the operative position of the pump.

Although in the drawing the aperture 12 extends radially in the wall ofthe pump casing, it will be appreciated that it may also be provided inthe upper cover 3. This is shown by broken lines in the figures.

The pump shown in the figure is of the type which is immersed in aliquid bath with its shaft in a vertical position. Thus the liquid hasready access to the impeller through the supply apertures 6. A dischargepipe through which the delivered liquid is discharged, is connected tothe liquid discharge spout 11. The mixture of liquid and vapour flowingout of the aperture 12 returns to the liquid bath, from which the vapourcan escape. As an alternative, the pump may be used without beingimmersed in a liquid bath. For this purpose 3 a supply pipe for theliquid to be pumped is connected to to the supply aperture in the pumpcasing. In this event, the liquid flowing through the aperture 12 may bereturned to the supply pipe through a pipe which may include a vapoureliminator.

The diameter of the aperture 12 need not be large. It has been foundthat an aperture having a diameter of the order of 3 to 5 mm. provides aflushing action such that there is no inconvenient vapour formation inthe pump.

A pump having a raising height of 6 meters and a delivery of 150 litresper hour operates satisfactorily with an aperture having a diameter of 4mm. The surprising feature of this pump consists in that the pumpempties the bath in which it is immersed until the level of the liquidhas fallen to the supply aperture of the pump. Such a result isunobtainable with any of the known pumps.

In the figure only a single aperture is shown. It will be appreciatedthat the same results may be achieved with several apertures and alsothat the location of the aperture may be slightly varied.

FIGURES 3 and 4 shows a multi-stage centrifugal pump. This pump has acasing 21 built up of several parts. To the upper part of the casing 21is secured a guiding means 24 for the pump shaft 25. The guiding means24 is provided with supply apertures 26 for the liquid to be pumped. Thepump shaft 25 may be driven by a driving device, for example, anelectric motor (not shown). The pump shaft 25 carries a number ofimpellers 27 which are each acommodated in a separate chamber in thecasing 21. Each impeller 27 is provided With a duct 28 for the liquidwhich extends from the inner circumference of the periphery. Eachimpeller is surrounded along the periphery by a guid-s duct 30 for aliquid. Each guide duct communicates with the suction end of the nextimpeller through a slit 31 between the impeller surrounded by therelevant duct and the Wall of the chamber in which the said impellerrotates. Guide vanes 32 for the liquid are arranged in the slits 31.

An aperture 33 is provided in the outer wall of the guide ductsurrounding the first impeller through which the liquid passes.

This aperture 33 opens into an annular recess 35 which merges into theliquid guide duct 30. The annular recess communicates through a slitbetween the impeller 27 and the upper wall of the pump with the suctionend. Although the drawing shows only a single aperture 33, severalapertures 33 may open into the recess 35. Such a recess may also beprovided in the pump of FIG. 1. The annular recess provided in the upperportion of the liquid guide duct ensures satisfactory flushing of thepump because most vapour collects in the upper part of the duct. Viewedperipherally the aperture may be located arbitrarily. It has been foundthat the provision of an aperture in the duct surrounding the firstimpeller through which the liquid passes suffices to counteract theadverse influence of the formation of vapour bubbles in the pump. Theother ducts need not be provided with flushing apertures.

The pumps according to the invention are particularly suitable forpumping comparatively small amounts of liquefied air, oxygen, nitrogen,and so on.

What is claimed is:

A multistage vertically arranged centrifugal pump comprising a sectionalcasing divided horizontally with respect to the vertical axis of thepump, each section having a pumping chamber housing an impeller thereinand in communication with the next succeeding stage, the pumping chamberin the first casing section being defined by a substantially flat uppersurface and a substantially flat lower surface spaced axially from theupper surface and connected to the upper surface by an annularcontinuous surface defining a collecting channel, said first sectionhaving a central inlet communicating with the first impeller, said firststage impeller having a plurality of radially extending passagescommunicating with the central inlet and the collecting channel, theimpeller having a continuous outer periphery terminating radiallyinwardly of the periphery of the collecting channel, an annular axiallyextending groove in the fiat upper surface of the first stage collectingchamber adjacent the periphery of the impeller, whereby on rotationthereof the pumped fluid received by the annular collecting chamber isseparated into high and low density fluid, and low density fluidcollects in said annular groove in the upper surface and high densityfluid passes downstream to the next adjacent stage, a plurality of axialapertures in said upper wall of the first stage communicating with saidannular groove whereby the collected low density fluid is free to escapefrom the annular groove.

References Cited by the Examiner UNITED STATES PATENTS 885,108 4/1908Trent 103-103 1,988,875 l/ 1935 Saboris 103103 2,216,542 10/ 1940 Paige103-113 2,291,138 7/1942 Blom 103-413 2,388,839 11/1945 Stepanoif 1031132,416,031 2/ 1947 Wade 103-113 2,480,435 8/ 1949 Aspelin 103--1082,812,111 11/1957 Wright et al. 103108 2,829,598 4/1958 Zimmermann etal. 103-113 2,845,870 8/1958 Lock 103-413 FOREIGN PATENTS 188,54711/1922 Great Britain.

886,248 1/ 1962 Great Britain.

154,413 5/ 1956 Sweden.

DONLEY J. STOCKING, Primary Examiner.

JOSEPH H. BRANSON, I12, KARL I. ALBRECHT,

Examiners.

